As a backlight for a LCD (Liquid Crystal Display) panel (e.g., car navigation monitor), currently, a cold cathode fluorescent lamp (CCFL) is chiefly used; however, from viewpoints of an Hg-free movement and advantages in high brightness, energy saving, longevity and the like, in recent years, a white LED (Light Emitting Diode) is in practical use; and various technologies are disclosed and proposed for a LED driving device (so-called LED driver) that performs drive control (e.g., see a patent document 1).    Patent document: JP-A-2007-13183